430+hp 340 possibilities

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Lurbieloo

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Hi guys, I’m going to tear down my 340 this winter and am wanting to rebuild it to get somewhere around 430-450 hp. Wondering if anyone has achieved these numbers or close to using stock heads (ported)as budget will be an issue for me. Thanks.
 
It will be a stretch getting there with stock compression and heads. If you increase the compression considerably, port the heads, and choose the proper camshaft it's possible. 65'
 
Speed is expensive. How fast do you want to go? 430 HP is achievable. Compression is very important. Selecting the right cam is critical too. My advice: read the books. There are many knowledgeable people here but the problem is that everyone has their own way of selecting parts and building engines. This can become confusing to you. Do your own research and learn the engineering. It's time consuming but well worth it. Learning about cam timing, valve timing and how it affects compression ratio is VERY important. Head gasket thickness, deck height, etc. There's a lot to learn. Good luck.
 
Much depends on your head flow.

Edelbrock claims 417hp with there RPM package. A basic copy of there package with exception to there cam and minor attention to the heads will get you there. I just researched the compression ratio Edelbrock said there 340 was at. It was a 9.5-1. A true 10.1 - 10.5-1 is what I did compression wise on my 340.

Camshaft wise, I’d look for a similar duration cam but with a better lobe and more lift to take advantage of the cylinder heads air flow. Edelbrock did not do this.

(FWIW - Below is the cam I chose to run in my 340. A fair bit more aggressive than Edelbrock’s cam by 7*’s @050 on the intake. This is a one step up in cam duration. I had Comp move the 110 to a 108. It is being used with ProMaxx CNC ported heads.)

However, since you have ported heads, knowing how well they match up against the Edelbrock heads is something worth knowing & addressing to make them equal or better.

Your power level is easy to obtain as long as the parts are up to task.

792871BE-43A0-4001-AACF-617300B50D88.jpeg


Edelbrock 340 RPM cam specs below;

Chrysler 340 RPM cam
Operating Range 1500-6500 RPM
Duration Advertised 308° Intake/318° Exhaust
Duration @ .050'' 234° Intake/244° Exhaust
Lift @ Valve .488'' Intake/.510'' Exhaust
Lift @ Cam .325'' Intake/.340'' Exhaust
Lobe Separation Angle 112°
Intake Centerline 107°
 
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Lurbieloo said:
Hi guys, I’m going to tear down my 340 this winter and am wanting to rebuild it to get somewhere around 430-450 hp. Wondering if anyone has achieved these numbers or close to using stock heads (ported)as budget will be an issue for me. Thanks.
Click to expand...
Are you going to do the work? Or are you going to have a professional engine builder do it?
 
I used this cam too in my 340. I bored and stroked it to a 371ci. I love that cam. It makes a ton of power.



Edelbrock 340 RPM cam specs below;

Chrysler 340 RPM cam
Operating Range 1500-6500 RPM
Duration Advertised 308° Intake/318° Exhaust
Duration @ .050'' 234° Intake/244° Exhaust
Lift @ Valve .488'' Intake/.510'' Exhaust
Lift @ Cam .325'' Intake/.340'' Exhaust
Lobe Separation Angle 112°
Intake Centerline 107°[/QUOTE]
 
8formulas said:
I used this cam too in my 340. I bored and stroked it to a 371ci. I love that cam. It makes a ton of power.
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Nice! Also thanks. I choose and modified the cam in a minor way to be a fun street engine that would not rev to high in making power. I’ve used cams in the upper 240 duration area and they can be a little piggish on the street. I also entertained cams in the mid and upper 230’s.

Truth be told, after seeing a few engine masters shows, the cam made power right about where I wanted my engine to perform in. It’ll be in a lightened ‘71 Duster for a spell before I move the top end over to my lightened ‘79 Magnum.

The 340 will then be transformed for a resto-ish engine for my ‘73 Cuda. It’ll look right but be the actual engine it was born with, something I never got with the E body.

How did you do your engine and drive train?
 
430 to 450hp out of a stock headed, stock stroke 340 doesn't sound like a budget build.

Having been through doing a set of iron heads over including porting and oversixed valves and also having bought aluminum heads OOTB, stage I, II and III aluminum heads. Just be sure to weigh you options wisely. Stock heads are expensive to mess with and in the end you often have an unrepairable sub par piece and spent as much or more money.
 
Lurbieloo said:
Hi guys, I’m going to tear down my 340 this winter and am wanting to rebuild it to get somewhere around 430-450 hp. Wondering if anyone has achieved these numbers or close to using stock heads (ported)as budget will be an issue for me. Thanks.
Click to expand...

IMHO, unless I just had to have factory heads I'd buy aluminum before I spent much money having iron heads ported. Not saying you can't reach your goal with the factory heads but I'd prefer a closed chamber aluminum head.
 
Well I can give you some actual track fwhp no's from my '71 street/strip 340 Cuda I ran back in 1985>
T/A 2.02 heads unported, stock v/job, cleaned up, valves just ground in.
stock '71 replacement trw pistons with .039 fel-pro's so around 9.7:1?
1.3/4" hedman race hdrs
DC. .590" [email protected] sft cam
Strip dominator, +2" open spacer+ modded 850DP
car ran a best of 12.40@108 NA at approx 3550@the line = 367fwhp +/- a few.
4200stall and 4.30 gearing on stock springs....just some info that may be of some help.
 
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I agree with the two posts above.
But he did mention he has ported iron heads already.
Or am I reading it wrong?
I wouldn’t port iron heads unless there is a reason. Cost is not one of them.
 
if you are going to be buying pistons for your rebuild. Checkout my for sale thread.
8 Custom Forged Diamond Pistons 4.06 Bore, 10.5 compression
(compression distance 1.910 1/16, 1/16, 3/16 ring pack .927 pins)
Only used for about 100 street miles then built a 416 stroker wanted more torque and power.
 
Ok. Maybe I can clarify things (or my idea) a little. The car is a 1970 duster 340. 4 spd 3:55 gear. Numbers matching engine. Still has good compression across the board. (I’ve read they are a 10.25:1 engine already?) so I already own a set of J heads with the 2:02, 1.6 valves that are ported by a speed shop. 5 angle valve job, stock pistons and rods, Doug’s headers, i have a victor junior intake and an LD 340 intake to choose from, a good 750 double pumper for a carb. I haven’t chose a cam yet but was wondering if those numbers are achievable or am I dreaming to hit that? If I have to buy pistons etc should I just go with the stroker option?
 
Port hell outta some stock heads, 2.02/1.60 valves, moderate solid flat tappet, Trick Flow heads. Oh yeah and a 4" crankshaft.
 
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Lurbieloo said:
Ok. Maybe I can clarify things (or my idea) a little. The car is a 1970 duster 340. 4 spd 3:55 gear. Numbers matching engine. Still has good compression across the board. (I’ve read they are a 10.25:1 engine already?) so I already own a set of J heads with the 2:02, 1.6 valves that are ported by a speed shop. 5 angle valve job, stock pistons and rods, Doug’s headers, i have a victor junior intake and an LD 340 intake to choose from, a good 750 double pumper for a carb. I haven’t chose a cam yet but was wondering if those numbers are achievable or am I dreaming to hit that?
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Again, it depends on the level of porting done.
Again, the amount of air the heads flow need to be known.
I’d use the LD-340.
 
I would find a 360 and pull the original 340 out of the car and store it. Then ask “can I get 400-450 hp out of my 360 with cast iron heads?” Yes you can, not really cheap though.
 
Hot Metal said:
Well I can give you some actual track fwhp no's from my '71 street/strip 340 Cuda I ran back in 1985>
T/A 2.02 heads unported, stock v/job, cleaned up, valves just ground in.
stock '71 replacement trw pistons with .039 fel-pro's so around 9.7:1?
1.3/4" hedman race hdrs
DC. .590" [email protected] sft cam
Strip dominator, +2" open spacer+ modded 850DP
car ran a best of 12.40@108 NA at approx 3550@the line = 367fwhp +/- a few.
4200stall and 4.30 gearing on stock springs....just some info that may be of some help.
Click to expand...
Though it's a little dated I love that 590 it's a badass stick it in there advanced to like 101
 
MOPAROFFICIAL said:
Though it's a little dated I love that 590 it's a badass stick it in there advanced to like 101
Click to expand...

Yep it ran real good even in my motor, and on the street I found it quite mild tbh albeit I had that 4200TA verter, only downside was I only had 26.5" tall street tyres@the time, there was a tall truck type street tyre that just came out then but didn't have the money to buy them so with the 4.30's 55mph was 4k rpm on the freeway, put up with it but was a bit annoying, stopped going anywhere far after that, kept it around town. My mate went 10.1's in a 3150lb 440 dart with that .590 cam in@104.
 
wondering if those numbers are achievable or am I dreaming to hit that?
Click to expand...

I’m going with.....dreaming a little.

For the type of application you’re talking about, don’t focus on the power output.
Select parts that are complimentary to how the car will be used, the gearing, etc.
Make it so all the parts are “on the same page”....... and then the power is what it is.

I built an iron headed 450hp stock stroke 340 years ago....... it wouldn’t really have been suitable in a street car with closed exhaust and 3.55’s.

It did go 11.60’s in a 68 B body though.
 
Your horsepower goals are achievable but looking at your build everything looks good except for your rear end ratio. If you Cam up that's not enough gear and if you cam to that gear ratio I don't think you're going to achieve the power that you're wanting. That's the thing about a 340 cubic inch is you need to wind it, your setup screams for a fairly aggressive Cam and 410 gears
 
PRH said:
I’m going with.....dreaming a little.

For the type of application you’re talking about, don’t focus on the power output.
Select parts that are complimentary to how the car will be used, the gearing, etc.
Make it so all the parts are “on the same page”....... and then the power is what it is.

I built an iron headed 450hp stock stroke 340 years ago....... it wouldn’t really have been suitable in a street car with closed exhaust and 3.55’s.

It did go 11.60’s in a 68 B body though.
Click to expand...
 
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